Treatment of steel articles



Patented Apr. 15, 1947 2,418,935 TREATMENT OF STEEL ARTICLES Gilbert E. Hutchinson, Bridgeport, Conn., 115- signor to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware No Drawing. Application August 26, 1943, Serial No. 500,071

can be made of improved resistance to corrosion by exposing a steel article which has moisture absorbed or adsorbed on the surfaces thereof to the vapors of a hydrocarbon-silicon halide and removing the halogen acid formed before it has had suflicient time to appreciably, react with the steel.

The useful hydrocarbon silicon halides have the general formulae:

wherein R, R, and R" are lower alkyl radicals, e. g., of 1 to 4 carbon atoms or an aryl radical of the :benzene series, e. g., phenyl, tolyl, mesityl, and X is a halogen, e. g., fluorine, chlorine, bromine and iodine; and are capable of vaporization at room to moderate temperatures.

The compounds in general should have an appreciable vapor pressure at room temperature; however, since they may be used at reduced pressures and/or elevated temperatures, it suffices if the compounds provide an appreciable amount of vapor at the temperature and pressure used. The preferred compounds include the methyl and ethyl chlorides including those containing from 1 to 3 methyl or ethyl groups and 1 to 3 chlorine atom and mixtures of such compounds.

The hydrocarbon-silicon-halide compounds, as exemplified by dimethylsilicon dichloride, appear to react during the process with water in accordance with the equation:

Si HOH Si 21101 C a 01 CH; OH

and to further react as a result of heating or in the presence of an acid to form condensation products in accordance with the equation:

(heat) and/or (acid) CH: OH

HO-SKCHah-b-SKCHzh-OH 11.0 Further condensation occurs by the same mecha- 4 Claims. (Cl. 117-49) nism whereby higher linear silicone polymers are formed.

It has been further found that the nature of the surface of the steel articles has a definite relationship to the corrosion resistant properties of the final article. To be more specific, it has been found that steel articles which have a thin, porous coating of insoluble metal compounds, e. g., insoluble metal phosphates, when treated with the hydrocarbon-silicon halides in the manner herein taught, acquire enhanced corrosion resistant properties to weathering and atmospheric conditions.

The art of forming thin porous coatings on steel articles is well-developed and many practical procedures are practiced commercially. The socalled Bonderite and Parkerite coatings, for example, constitute suitable undercoats. The latter coatings are phosphate coatings, e. g., normal and secondary phosphates of iron and manganese or zinc. The formation of such coatings can be attained by treating a steel article by immersion in an aqueous solution of zinc or manganese dihydrogen phosphate and phosphoric acid, whereby the following reactions are believed to occur:

or combined- HaPO4 3MnHPO4 2Fe (H20) Mn3(PO4)2 zreuroi 2H,

Suitable processes for producing steel articles with thin porous phosphate coatings are described in U. S. Patents 1,167,966, 1,842,085 and 2,303,242. They may vary somewhat in thickness and in crystal structure or configuration.

The steel surfaces, however, may have other types of thin porous coatings of insoluble metal salts or oxides. For instance, a chemical black iron oxide layer produced by means of an alkaline oxidizing solution, or an oxide layer produced by treating a steel article in an oxidizing flame, can be used. In addition, a thin porous layer of copper and/or copper compounds, such as the so-called Cuprodine layer made by immersing a steel article in a solution of the following composition, can be used:

Copper sulphate pentahydrate 1bs 0.250 Sodium chloride do 0.083 Sulphuric acid-66 Baum gals 0.030 Inhibitor A oz.. 0.05 Water to make gals 1.0

1 Inhibitor A (U. 8. 2,217,921) is a concentrated solution of the reaction product of orthotoludidine and formaldehyde in hydrochloric acid containing 40% active inhibitor by weight.

It has been determined that a steel article -hav ing a thin, porous coating of insoluble metal compounds of the above type and especially metal phosphates, can be advantageously made of enhanced corrosion resistance by passing the metal article at room temperature through a steam chamber or a chamber filled with water vapor, then exposing the article to vapors of a hydrocarbon-silicon halide or a mixture of hydrocarbon-sllicon halides of the above-described properties for a period of about /2 to about 5 minutes at room temperature and then heating the article to a temperature high enough to drive oil the acid formed for a period of 5m 100 minutes and preferably from to 20 minutes. A temperature of 90 C. to 150 C. constitutes a practical and 110 to 140 C. a preferred range.

Example A steel shell casing which has been given a Parkerizing" or Bonderizing treatment, as described above, to form a thin porous coating of insoluble iron phosphates is passed at room temperature into a steam chamber, then exposed to the vapors of a mixture of methyl-silicon chlorides, including dimethylsilicon dichloride, methylsilicon trichloride and trimethylsilicon chloride, for 2 minutes and then heated to a temperature of about 130 C. with a current of hot air for 10 minutes. The resulting article is decidedly more resistant to direct exposure to wind, rain, hail, sleet, snow and light and salt spray than a steel shell casing of the same type which was not given the latter treatment.

It has been found that the heating step is essential and the prompt removal of the halogen acid vital to a successful and practical practicing of the invention. Steel articles which are not treated as herein taught or washed with water or an aqueous alkali solution after exposure to the vapors of the hydrocarbon-silicon halides, for example, rust about as rapidly as bare steel.

Steel articles in general can be treated by the processes hereof. It is particularly useful in the fleld of small arms ammunition components, e. g., .22, .30, .45 and .50 caliber steel cases, steel projectile components, steel shot shell heads, etc. The latter articles can be treated in a manner similar to that of the example. Any of the hydrocarbon-silicon halides, however, can be substituted. Suitable additional compounds include the propyl, butyl, phenyl and Dhenylmethyl silicon chlorides.

This invention has the advantage that it can be carried out with simple, inexpensive equipment. A further advantage is that it can be accomplished in a relatively short time. Another advantage is that it requires little supervision and is easily controllable. A still further advantage is that it can be used with small or large articles with uniform results. Another advantage resides in the fact that it can be carried out with large or small scale operations.

The steel articles treated by the above method are resistant to ordinary weathering conditions, and quite resistant to exposure to salt water spray. The latter fact is of. importance for steel ammunition.

As many apparently widely difierent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof ex- ,cept as defined in the appended claims.

I claim:

1. A method for improving the corrosion resistance of steel articles, which comprises sub- Jecting a steel article to a moisture vapor treatment, subjecting the moisture vapor coated steel article to the vapors of a volatile hydrocarbon silicon halide to form a hydrocarbon silicon coating thereon, and then immediately heating to a temperature of between 90 C. and 150 C. with a current of hot air for about 5 to 100 minutes to drive off the acid formed by the reaction between the vapors of the hydrocarbon silicon halide and the moisture vapor, and to condense the reaction product into a high linear silicone polymer.

2. A method for improving the corrosion resistance of steel articles, which comprises subjecting a steel article to a moisture vapor treatment, subjecting the moisture vapor coated steel article to the vapors of methyl silicon chloride for approximately /2 to 5 minutes, and then immediately heating to a temperature of between C. and 150 C. with a current of hot air for about 5 to minutes to drive oil the acid formed by the reaction between the vapors of the methyl silicon chloride and the moisture vapor, and to condense the reaction product into a high linear silicone polymer.

3. A method for improving the corrosion resistance of steel articles, which comprises passing a steel article into a zone containing water vapor, removing the article from said zone, subjecting the article at room temperature for a period of about 2 minutes to the vapors of methyl silicon chloride, and then immediately heating the article to a temperature of between about C. and C. for a period of about 10 to 20 minutes to drive off the acid formed by the reaction between the vapors of the methyl silicon chloride and the water vapor, and to condense the reaction product into a high linear silicone polymer.

4. A method for improving the corrosion resistance of steel articles, which comprises coating 2. steel article with a thin adherent porous surface composition composed of insoluble phosphates, passing the so-coated steel article intoa zone containing water vapor, removing the article from said zone, subjecting the article at room temperature for a period of about two minutes to the vapors of methyl silicon chloride, and then immediately heating the article to a temperature of between about 110 C. and 140 C. for a period of about 10 to 20 minutes to drive off the acid formed by the reaction between the vapors of the methyl silicon chloride and the water vapor, and to condense the reaction product into a high linear silicone polymer.

GILBERT E. HUTCHINSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,258,218 Rochow Oct. 7, 1941 2,306,222 Patnode Dec. 22, 1942 OTHER REFERENCES King, "Paint Manufacture, May 1931, page 55. (Photostat in Div. 38.) 

